Jellyfish are among the ocean’s strangest and most ancient animals. Their soft, translucent bodies are made mostly of water, allowing them to drift through the sea with very little energy.
They belong to the phylum Cnidaria, a group that also includes corals and sea anemones. Their familiar bell-shaped swimming form is known scientifically as a medusa.
Despite their appearance, jellyfish have no brain, heart, bones or lungs. Instead, they rely on a simple nerve network that allows them to sense changes in light, movement and their surroundings.
Their most remarkable feature is found in their tentacles. Jellyfish have specialized stinging structures called nematocysts, contained within cells known as cnidocytes. These microscopic structures can fire like tiny harpoons, injecting venom that helps jellyfish capture prey and defend themselves.
The word medusa used by zoologists comes from the mythological Greek figure Medusa, whose head was covered with snakes — a resemblance to the flowing tentacles of a jellyfish.
Jellyfish may look fragile, but they are highly successful marine animals. They live throughout the world’s oceans, from shallow coastal waters to the deep sea, and they also serve as food for animals including sea turtles and fish.
The “immortal jellyfish” (Turritopsis dohrnii) can reverse its life cycle, transforming from an adult jellyfish back into a juvenile polyp stage. This unusual ability has earned it the nickname “biologically immortal,” although it can still die from disease, injury or predators.
Sources: NOAA | NOAA Fisheries
By NJ RADAR Team